//
// Created by ✎﹏ℳ๓独赏 ☆独醉 on 2023/3/2.
//
#include <stdio.h>
int total = 0;
int sum(int i){
    if(i==0){
        return 0;
    }else{
        return total = i + sum(i-1);
    }
}
int main(){
    int i = 0;
    scanf("%d",&i);
    printf("%d",sum(i));
    return 0;
}